JP2003198524A - Cryptographic key recovering device, repeater and depository device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the owner of a cryptographic key to recover the unavailable cryptographic key by himself/herself. <P>SOLUTION: In a cryptographic key recovery system 10, respective elements required for recovering the cryptographic key transmitted from a cryptographic key recovering device 1 are finally transmitted to a depository device 2 via a plurality of repeaters 31 and 32. Besides, in the repeaters 31 and 32, enciphering processing of the respective elements is performed so that information to be transmitted to the depository device 2 can become encrypted information which can not be deciphered by the depositing device 2. Therefore, the depository device 2 can not recover the cryptographic key of the cryptographic key recovering device 1 from the deposited information. Besides, the repeaters 31 and 32 deal with only one of a plurality of elements required for recovering the cryptographic key so that the cryptographic key can not be recovered from one element. Thus, the cryptographic key can be prevented from being recovered by a third person and only the cryptographic key recovering device 1 as the owner of the cryptographic key can recover the cryptographic key. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encryption key recovery system for recovering an encryption key, and more particularly to an encryption key recovery system which enables an owner of an encryption key to recover the lost encryption key. .

[0002]

2. Description of the Related Art Currently used encryption methods are:
There are common key cryptography and public key cryptography. The common key cryptosystem is an encryption system in which the same key is used for encryption and decryption.On the other hand, the public key cryptosystem generates a pair of private key and public key, It is held only by the owner and the public key is disclosed to a third party. Then, the public key is used for data encryption and the private key is used for decryption.

[0003]

By the way, in the above-mentioned common key cryptosystem, when the storage device or the storage medium storing the common key used for encryption or decryption is damaged, etc. Since the key cannot be used, the inconvenience occurs that the information cannot be encrypted or decrypted.
Similarly, in the public key cryptosystem, if either the private key or the public key cannot be used, the data cannot be encrypted and the encrypted data cannot be decrypted, which causes inconvenience.

The present invention has been made in view of such circumstances, and the owner of the encryption key can recover the encryption key that cannot be used by itself, the encryption key restoration device, the relay device, and the depository device. The purpose is to provide.

[0005]

In order to achieve the above object, the present invention provides an encryption key recovery device for recovering an encryption key,
Used in an encryption key recovery system including an escrow device that stores a plurality of elements necessary for recovering an encryption key, and a relay device that relays transmission / reception of information between the encryption key recovery device and the escrow device. In the encryption key recovery device described above, a plurality of elements required for recovering the encryption key are generated, the elements are transmitted to separate relay devices, and when the encryption key is recovered, There is provided an encryption key recovery device characterized by transmitting a return request of the element to a relay device and recovering an encryption key based on the plurality of elements returned from the relay device.

In the encryption key recovery device of the present invention,
The element is characterized by being predetermined information or information generated based on an encryption key and the predetermined information. Specifically, the encryption key recovery device converts the encryption key and the predetermined information by a predetermined conversion method set in advance to obtain the generated information. It is preferable to use exclusive OR as the predetermined conversion method. In this case, the encryption key recovery device obtains the generated information that is the exclusive OR of the encryption key and the predetermined information, and determines the predetermined information and the generated information as an element used to recover the encryption key. The predetermined information may be any information, and the predetermined information may be a plurality of independent (individual) information.

Further, the encryption key recovery device of the present invention is characterized in that the element is encrypted by using the public key of the depositor, and each element after encryption is transmitted to a separate relay device. .

Further, in order to achieve the above object, the present invention provides an encryption key recovery device for recovering an encryption key, a depository device for storing a plurality of elements necessary for recovering the encryption key, and the encryption device. A relay device used in an encryption key recovery system comprising a key recovery device and a relay device for relaying transmission / reception of information between the escrow device, which is required for recovering an encryption key from the encryption key recovery device. When the element which becomes the following is received, the received element is encrypted by using a predetermined encryption method, the encrypted element is transmitted to the escrow apparatus, and the element return request is received from the encryption key recovery apparatus. In this case, there is provided a relay device characterized by acquiring a corresponding encryption element from the depository device, decrypting the encryption element, and transmitting the decrypted encryption element to the encryption key recovery device. In addition,
An example of the predetermined encryption method is a public key encryption method. That is, the relay device encrypts the element with the public key and transmits the encrypted element to the depository device, while the encrypted element obtained from the depositor device is decrypted with the secret key and transmitted to the encryption key recovery device.

Further, in order to achieve the above object, the present invention provides an encryption key recovery device for recovering an encryption key, a depository device for storing a plurality of elements necessary for recovering the encryption key, and the encryption device. The escrow device used in an encryption key recovery system comprising a key recovery device and a relay device for relaying transmission / reception of information between the escrow device, wherein the information necessary for recovering an encryption key is relayed. When received from a device, the received information is stored, and when the request to return the information is received from each relay device, the information is returned to each relay device. I will provide a. The encryption key is, for example,
It is a secret key in the public key cryptosystem.

Further, the escrow apparatus of the above invention, when the received information is encrypted using its own public key,
After the information is decrypted by its own private key, the information is transmitted to the relay device.

According to the encryption key recovery device, the relay device and the escrow device of the present invention, first, at the time of depositing information, the encryption key recovery device generates a plurality of elements necessary for recovering the encryption key. , And transmits each generated element to a separate relay device. In addition, the relay device encrypts each received element by a predetermined encryption method, and transmits the encrypted element to the depository device. Then, the depository device stores the element received from each relay device, that is, each element encrypted by each relay device.

As a result, at the time of depositing the information, each relay device can receive only one of a plurality of elements required to recover the encryption key.
It is possible to prevent the encryption key from being recovered by the relay device.
Also, the depository device receives each element required for recovering the encryption key from each relay device. However, since each of these elements is encrypted by the relay device, the depositary device decrypts these information. Can not do it. This makes it possible to prevent the recovery of the encryption key by the depository device.

On the other hand, at the time of recovering the encryption key, the encryption key recovery device sends a request for returning the element to each relay device. As a result, each relay device that has received the return request requests the depositor device to return the corresponding element. The depository device that has received the request from each relay device is
The encrypted element received from each relay device is returned to each relay device. Upon receiving the encryption element, the relay device decrypts the encryption element and returns the decrypted element to the encryption key recovery device. Thereby, the encryption key recovery device can acquire each element generated by itself and can recover the encryption key based on these elements.

Thus, even when the encryption key is restored,
Since the relay device can handle only one element among all the elements necessary for recovering the encryption key, it is impossible to recover the encryption key.

Therefore, according to the present invention, it is possible to prevent the encryption key from being recovered by another person. Thereby, the leakage of the encryption key can be prevented, and the security of the encrypted data can be maintained sufficiently high.

Further, the encryption key recovery device encrypts each element with the public key of the deposit device, and transmits the encrypted element to each relay device, so that the relay device stores the encryption key at the time of depositing the information. Of the multiple elements needed to restore, only one element can be handled, and further,
Since this one element is the information encrypted with the public key of the depository device, it becomes possible to further prevent the recovery of the encryption key by the relay device. This makes it possible to maintain high security when depositing the information required to recover the encryption key.

[0017]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are diagrams showing the configuration of an encryption key recovery system according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the encryption key recovery system 10 is required to recover the encryption key recovery device 1 which is the owner of the encryption key and the encryption key deposited from the encryption key recovery device 1. It is composed of a escrow device 2 that stores elements and a plurality of relay devices 31 and 32 that relay communication between the encryption key recovery device 1 and the escrow device 2. The depository device 2 also includes a storage device 21 for storing the information received from each relay device, that is, an encryption element required to recover the encryption key of the encryption key device 1. The encryption key in this embodiment is a secret key in the public key cryptosystem.

Next, the operation of each device constituting the encryption key recovery system 10 having the above configuration will be described with reference to FIGS. 1 and 2.

(A) At the time of depositing information Hereinafter, the flow of information at the time of depositing information in the encryption key recovery system 10 will be described with reference to FIG.

First, the encryption key recovery device 1 has information necessary for recovering the encryption key (hereinafter referred to as an element).
To generate. Specifically, the encryption key recovery device 1 obtains the exclusive OR of its own encryption key S and the predetermined information K1, and the generated information K2 obtained as a result and the predetermined information K1 are used as the encryption key. Determine S as the factor needed to recover. Note that K2 = S (+) K1. here,
(+) Indicates exclusive OR.

Next, the encryption key recovery device 1 uses each element K
1, K2 is encrypted with the public key Dpk of the depository device 2,
The encryption element Dpk (K1) and Dpk (K2) are obtained. Then, each encryption element Dpk (K
1) and Dpk (K2) are provided as separate relay devices 31 and 3 respectively.
Send to 2. Here, the encrypted element Dpk (K1) is transmitted to the relay device 31, and the element Dpk (K2) is transmitted to the relay device 32. At this time, the identification information P assigned to itself (encryption key recovery device 1) is added to the encrypted element to be transmitted and transmitted.

As a result, the relay device 31, which has received the encryption element Dpk (K1) from the encryption key recovery device 1, further encrypts the received encryption element Dpk (K1) with its own public key Bpk and encrypts it. The conversion factor Bpk (Dpk (K1)) is obtained. Then, the self-identification information Q, that is, the identification information of the relay device 31 is added to the encrypted element Bpk (Dpk (K1)) and transmitted to the depository device 2 (step SP3). As a result, the information transmitted from the relay device 31 has the encrypted element Bpk (D
information "Bpk (Dpk (K1)) in which the identification information of the encryption key recovery device 1 and the identification information of the relay device 31 are added to pk (K1)".
1)) P, Q ”.

Further, the encryption element D from the encryption key recovery device 1
Upon receiving pk (K2), the relay device 32 encrypts this element with its own public key Cpk and encrypts it with the encrypted element Cpk (Dpk (K
2)) is obtained, and its own identification information R is added to this information and transmitted to the depository apparatus 2 (step SP4). This allows
The information transmitted from the relay device 32 is the encryption element Cpk.
Information "Cpk" in which the identification information P of the encryption key recovery device 1 and the identification information R of the relay device 32 are added to (Dpk (K2))
(Dpk (K2)) P, R ".

Subsequently, the depository apparatus 2 operates the relay apparatuses 31,
Upon receiving each encryption element required for recovering the encryption key of the encryption key recovery device 1 from 32, these encryption elements are decrypted by the private key Dsk of its own, and “Bpk (K1)
P, Q "and" Cpk (K2) P, R "are obtained, and this information is stored in the storage device 21 (step SP5). Accordingly, the public key B of the relay devices 31 and 32 is stored in the storage device 21.
Elements K1 and K2 encrypted by pk and Cpk, respectively
Information is stored as deposit information.

(B) Request for Return of Deposited Information Hereinafter, the flow of information at the time of request for returned deposited information in the encryption key recovery system 10 will be described with reference to FIG.

When the encryption key S owned by itself is no longer usable for some reason, the encryption key recovery device 1 recovers the encryption key S by the relay device 31,
A request for returning elements necessary for recovering the private key S of itself is transmitted to 32 (steps SP6 and SP).
7). The identification information P of the self is added to the return request.

Upon receiving the request for returning the deposit information, each of the relay devices 31 and 32 transmits a request for returning the deposit information to the deposit device 2 (steps SP8 and SP9). The identification information of the encryption key recovery device 1 and the identification information Q and R of the relay devices 31 and 32 are added to the return request.

When the depository device 2 receives the return request for each depositary information from each relay device 31, 32, the depositor device 2 stores the encryption element corresponding to the identification information added to the return request in the storage device 21.
It is extracted from the deposit information stored in (step SP10). That is, the encryption elements to which the identification information P and the identification information Q and the identification information P and the identification information R are added are extracted from the storage device 21. As a result, the depository device 2
Is “Bpk (K1), P, Q” and “Cpk (K2), P,
R ”is extracted from the storage device 21.

Then, the obtained encryption element is transmitted to the relay device specified by the identification information added to the encryption element (steps SP11 and SP1).
2). As a result, “Bpk (K1), P,
“Q” is transmitted to the relay device 32 as “Cpk (K2), P, R”.

The relay device 31 receives the received encryption element Bpk.
(K1) is decrypted by its own secret key Bsk, and element K
1 and the information “K1,
P, Q ”to the encryption key recovery device 1 (step SP
13). On the other hand, the relay device 32 receives the received encryption element C.
pk (K2) is decrypted with its own secret key Csk to obtain the element K2, and the information "K2," which is the identification information added to this element
P, R ”to the encryption key recovery device 1 (step SP
14).

As a result, the encryption key recovery device 1 acquires the elements K1 and K2 from the relay devices 31 and 32. And
The elements K1 and K2 can be converted by exclusive OR to recover the secret key S. The recovery conversion formula at this time is S = K1 (+) K2.

As described above, according to the encryption key recovery system 10 according to the present embodiment, each element K necessary to recover the encryption key S transmitted from the encryption key recovery device 1.
1 and K2 are finally transmitted to the depository device 2 via the plurality of relay devices 31 and 32. In addition, the relay devices 31, 3
In No. 2, since the encryption processing of each element K1 and K2 is performed, the information transmitted to the depository device 2 is encrypted information that the depositary device 2 cannot decrypt. Therefore, the depository device 2 cannot recover the encryption key S of the encryption key recovery device 1 from the deposited information. Further, the relay devices 31 and 32 are
A plurality of elements K required to recover the encryption key S
Since only one element K1 or K2 of 1 and K2 is handled, the encryption key S cannot be recovered from one element. In addition, the relay devices 31 and 32 and the encryption key recovery device 1
Since the communication between and is performed through a communication path having an extremely high security, it is impossible for a third party to invade, and this also eliminates the risk of the encryption key recovery by the third party.

As described above, in the encryption key recovery system 10 according to the present embodiment, the device capable of recovering the encryption key is limited to the encryption key recovery device 1 which is the owner of the encryption key, so that a third party can be provided. It is possible to prevent the encryption key from leaking. As a result, the encryption key can be protected with extremely high security, and it becomes possible to prevent leakage of the data encrypted with the public key paired with this encryption key.

Further, since the information stored in the storage device 21 of the depository device 2 is added with the identification information of the sender of the information, it is possible to identify a plurality of information by this identification information. Become. Therefore, even if the deposit information is received from a plurality of encryption key recovery devices, each deposit information can be managed accurately.

The encryption recovery device, the relay device, and the depository device may each be realized by dedicated hardware, and programs for realizing the functions of these devices are respectively stored in a computer. Various processes may be performed by recording the program in a readable recording medium, reading the program recorded in the recording medium into a computer system, and executing the program. In addition,
The "computer system" here includes an OS and hardware such as peripheral devices.

The "computer-readable recording medium" is, for example, an optical disk such as a CD-ROM or M.
It refers to a magneto-optical disk such as O and MD, a magnetic storage medium such as HDD and FD, a portable recording medium such as a semiconductor memory such as a flash memory, and a storage device such as a hard disk built in a computer system. Further, the "computer-readable recording medium" is a volatile memory (RAM) inside a computer system which serves as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those that hold the program for a certain period of time are also included.

Further, the above program may be transmitted from a computer system that stores the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. Further, the program may be a program for realizing some of the functions described above. further,
It may be a so-called difference file (difference program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

In particular, a program for executing the function of the encryption key recovery device should be installed in a user terminal (for example, a personal computer, a mobile phone, a mobile terminal such as an information mobile terminal) to realize the above-mentioned function. Can be considered.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and includes a design etc. within the scope not departing from the gist of the present invention. Be done.

For example, in the above-described embodiment, the depository device 2 decrypts the information received from each of the relay devices 31, 32 with its own secret key Dsk and then stores it in the storage device 21, but instead of this, , The storage device 21 stores the encryption element that is still encrypted with the public key Dpk of the depository device 2, and when the request to return the encryption element is received from the relay devices 31 and 32, the corresponding encryption code is received. The encrypted element may be decrypted with its own secret key Dsk and then transmitted to each of the relay devices 31 and 32. Thereby, the safety of information leakage prevention can be further enhanced.

Further, in the above-described embodiment, the depository device 2
Has centrally stored the information necessary for recovering the encryption key. Instead of this, the relay devices 31, 3 are replaced.
The various elements received by the device 2 may be stored in a storage device (not shown) included in itself. That is, each element necessary for recovering the encryption key by each relay device in a distributed manner may be stored. In this case, each relay device 3
When there is a request to return the element from the encryption key recovery device 1, the reference numerals 1 and 32 refer to the element stored by the encryption key recovery apparatus 1 as the public key B of the element.
Each element encrypted with pk and Cpk, that is, Bpk
(Dpk (K1)), Cpk (Dpk (K2)) deposit device 2
(Identification information is omitted here).

The depository device 2 decrypts each received encryption element with its own secret key Dsk, and decrypts the encrypted encryption element Bpk.
(K1) and Cpk (K2) are set to the relay devices 31, 3 respectively.
Return to 2. As a result, the relay devices 31 and 32 decrypt the received encrypted elements with their own secret keys Bsk and Csk, and transmit the respective elements K1 and K2 to the encryption key recovery device 1.

The exclusive OR is the most effective conversion method used when the encryption key recovery device 1 generates an element, but the conversion method is not limited to this. That is, any conversion method may be used as long as the encryption key recovery device 1 can recover the encryption key based on the deposit information.

[0044]

As described above, according to the encryption key recovery device, the relay device and the escrow device of the present invention, the devices other than the encryption key recovery device, that is, the escrow device and the relay device are respectively owned by those devices. It becomes impossible to recover the encryption key from the information being processed. As a result, the device that can recover the encryption key is limited to the encryption key recovery device that is the owner of the encryption key, and it is possible to prevent the encryption key from being recovered by another person. Thereby, the leakage of the encryption key can be prevented and the security of the encrypted data can be sufficiently maintained.

Further, the encryption key recovery device encrypts the element with the public key of the depositor, and transmits each encrypted element to each relay device, whereby the security of the system can be further maintained high. Become.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an encryption key recovery system according to an embodiment of the present invention and a flow of information at the time of depositing information.

FIG. 2 is a diagram showing a configuration of an encryption key recovery system according to an embodiment of the present invention and a flow of information at the time of a request for returning deposit information.

[Explanation of symbols]

1 Encryption key recovery device 2 Depository equipment 21 storage device 31, 32 Relay device 10 Encryption key recovery system

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshinori Tanaka             2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo             Nutty Advance Technology Co., Ltd.             Inside the company (72) Inventor Masayasu Kumagai             2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo             Nutty Advance Technology Co., Ltd.             Inside the company (72) Inventor Kei Tachihira             2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo             Nutty Advance Technology Co., Ltd.             Inside the company F-term (reference) 5J104 AA31 MA05

Claims (6)

[Claims] 1. An encryption key recovery device for recovering an encryption key,
Used in an encryption key recovery system including an escrow device that stores a plurality of elements necessary for recovering an encryption key, and a relay device that relays transmission / reception of information between the encryption key recovery device and the escrow device. In the above encryption key recovery device, a plurality of elements required for recovering the encryption key are generated, the elements are respectively transmitted to different relay devices, and when the encryption key is recovered, An encryption key recovery device that transmits a return request of the element to a relay device and recovers an encryption key based on the plurality of elements returned from the relay device. 2. The encryption key recovery device according to claim 1, wherein the element is predetermined information or information generated based on an encryption key and the predetermined information. 3. The element according to claim 1, wherein the element is encrypted by using a public key of a depository apparatus, and each element after encryption is transmitted to a separate relay apparatus.
The encryption key recovery device described in 1. 4. An encryption key recovery device for recovering an encryption key,
Used in an encryption key recovery system including an escrow device that stores a plurality of elements necessary for recovering an encryption key, and a relay device that relays transmission / reception of information between the encryption key recovery device and the escrow device. When the relay device receives the element necessary for recovering the encryption key from the encryption key recovery device, the received element is encrypted using a predetermined encryption method, and the encryption element To the escrow apparatus, and when the element return request is received from the encryption key recovery apparatus, obtains the corresponding encryption element from the escrow apparatus, decrypts the encryption element, and recovers the encryption key. A relay device characterized by transmitting to a device. 5. An encryption key recovery device for recovering an encryption key,
Used in an encryption key recovery system including an escrow device that stores a plurality of elements necessary for recovering an encryption key, and a relay device that relays transmission / reception of information between the encryption key recovery device and the escrow device. In the depository device, when the information necessary for recovering the encryption key is received from the relay device, the received information is stored and a request to return the information is received from each relay device. In this case, the depository device is characterized in that the information is returned to each relay device. 6. When the received information is encrypted by using its own public key, the information is decrypted by its own private key and then the information is transmitted to the relay device. The deposit apparatus according to claim 5, characterized in that: